Residential wastewater treatment systems have become a popular alternative to septic tanks because they deliver cleaner water to the field. Some municipalities no longer permit traditional septic systems. Further, it is anticipated that municipal standards will continue to be more rigorous in the future. Because connecting a home to a city sewage system can be costly or simply unavailable, home wastewater treatment systems that are more effective than septic tanks will remain an attractive alternative and are expected to entirely replace the use of traditional septic tanks. Currently available home wastewater treatment systems are modeled after treatment processes employed by large central treatment plants, but are smaller and disposed underground.
Current home wastewater treatment processes mimic natural bacterial decomposition processes. Specifically, aerobic bacteria are utilized to digest and breakdown waste material in the water. The wastewater is aerated with an air compressor coupled to two or more diffusers spaced around the bottom of the treatment or aeration tank. Currently available diffusers include porous ceramic materials that are connected to the compressor by a flexible hose. The diffusers and compressor generate large quantities of small air bubbles which move upward through the wastewater. As the aerobic bacteria is naturally present in the wastewater, the bacteria multiply and flourish with the abundance of oxygen and food (waste material), resulting in the wastewater being converted to clear liquid and gas. Generally speaking, smaller bubbles provide better air-to-liquid contact and hasten the aerobic digestion process.
Currently available home wastewater systems can incorporate from one to three separate tanks. Referring to FIG. 11, aerobic bacterial purification takes place in an aeration tank 160. Raw sewage or wastewater may be received directly in the aeration tank 160 or in a separate pretreatment tank 170 where solid material is allowed to settle out or separate from the liquid. Liquid material may then be delivered from the pretreatment tank 170 to the aeration tank 160. Water from the aeration tank 160 may be delivered directly to the field or to a separate pump tank 180.
As shown in FIG. 11, the aeration tank 160 includes an aeration area 148 or space segregated by a clarifier cone 141 disposed within the aeration tank 160 which defines a clarifying area 149 or space. The clarifier cone 141 typically has an inverted frusto-conical shape. Either raw sewage from the home or liquid from the pretreatment tank 170 enters the aeration space 148 outside of the clarifier 141 where it is aerated and mixed with the aerobic bacteria. In addition to oxygenating the liquid in the aeration tank 160, the compressor 181 and diffusers 182 can also act to mix the material in the aeration space.
Hydraulic displacement causes the treated water to enter the clarifier 141. Due to the relatively calm conditions in the clarifier 141 and the upwardly sloping wall 144 of the clarifier 141, residual solid material drops downward through the open lower end or frustum 145 of the clarifier cone 141 and back to the aeration space 148 for further treatment. The remaining liquid material or effluent, upon reaching the outlet piping 139 disposed towards the wide upper end 142 of the clarifier 141, is clear and odorless. The material leaving the outlet 139 can be delivered to the holding or pump tank 180, delivered directly to a field through the line 191 for subsurface disposal or, in certain jurisdictions, may be discharged directly to a stream or pond or used for irrigation. A delivery pump is shown at 192.
Typically, a control panel is to used monitor the conditions within the tank(s). In current designs, both the control panel and compressor are disposed above ground for access and maintenance. Conventional wastewater treatment systems must be buried below ground a suitable distance away from the home or structure. The control panel and compressor are typically placed onto a wall of the home thereby requiring trenching for the electrical lines between the control panel and tank(s) as well as trenching for air lines between the compressor and the aeration tank. Alternatively, the compressor and a control panel can be located on the top of the aeration tank (see 181 in FIG. 11). In both designs, the compressor is disposed above ground, thereby generating unwanted noise or requiring relatively expensive compressors that ate selected for quiet operation.
Further, the use of currently available diffusers 182 is not without problems. Specifically, the porous ceramic diffusers need periodic maintenance or replacement, which requires the service personnel to pull the air lines connected to the diffusers upward out of the aeration tank. Gaining access to currently available home wastewater treatment tanks is also problematic as most systems include round lids or hatches with as many as a dozen bolts holding the lid or hatching place. Further, placement of the diffusers within the tank can be problematic as it may be difficult to adequately space the diffusers apart for thorough distribution of air bubbles and the diffusers are relatively inefficient in terms of mixing capabilities.
Another problem associated with current home wastewater treatment systems is associated with flooding. If the homeowner's yard or neighborhood floods, a multi-tank system can become buoyant and rise toward ground level. Thus, there is a need for a convenient means fox anchoring such as systems in place, particularly for areas which are prone to flooding.
Further, because a large hole is required to be excavated when home wastewater treatment systems are installed, the replacement and modification of such systems can be expensive. As wastewater treatment technology advances, there is a need for the ability to retrofit existing systems with improved technology thereby eliminating the need to replace systems altogether.